Semiconductor radiation detector and radiological imaging apparatus

ABSTRACT

A radiation imaging apparatus with high spatial resolution including semiconductor radiation detectors arranged on a wiring board capable of detecting γ-rays by separating their positions in the direction of incidence of γ-rays is provided. A semiconductor radiation detector is constructed by including five semiconductor devices made up of, for example, CdTe rectangular parallelepiped plates, a cathode electrode on one side of the semiconductor device, an anode electrode on the other side of the semiconductor device and an insulator for coating five semiconductor detection devices from the outside. The semiconductor radiation detector is mounted on a wiring board using an anode pin and a cathode pin.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor radiation detector,which allows semiconductor radiation detectors to be arranged in athree-dimensional direction and a radiation imaging apparatus using thesame.

A semiconductor radiation detector is provided with a semiconductordevice made of CdTe, CdZnTe, etc., and electrodes formed on both sidesof this semiconductor device designed to pick up electric chargegenerated when radiation such as X-rays or γ-rays enter thesemiconductor device by applying a bias voltage between these electrodesfrom the electrodes as a signal.

When a semiconductor radiation detector is used for a medical radiationimaging apparatus, etc., the semiconductor radiation detector isconnected on a wiring board to form a radiation detection section (seeJP-A-2003-84068 (paragraph 00024, FIG. 3), for example).

A PET (Positron Emission Tomography), which is a kind of a medicalradiation imaging apparatus, is intended to improve spatial resolution.However, the device described in JP-A-2003-84068 can detect γ-raysmainly on a plane of incidence of γ-rays (e.g., X-Y plane) by separatingtheir positions but cannot detect γ-rays in the direction of incidenceof γ-rays (e.g., Z-direction) by separating the positions. That is, thedevice cannot detect γ-rays by separating the positions in thethree-dimensional direction. Thus, it cannot improve spatial resolutionsufficiently.

It is an object of the present invention to provide a semiconductorradiation detector and radiation imaging apparatus capable of improvingspatial resolution.

SUMMARY OF THE INVENTION

A feature of a first embodiment of the invention for solving the abovedescribed problem is a semiconductor radiation detector comprising aplurality of semiconductor detection devices, each having an anodeelectrode on one side of a semiconductor device and a cathode electrodeon the other side, arranged in parallel and an insulator which coats atleast a portion of the semiconductor detection devices from the outside.This enables the semiconductor radiation detector to be arranged in anarbitrary position and its spatial resolution to be improved.

The semiconductor radiation detector preferably has a structure in whichinternal wiring is provided in the interior or on the surface of theinsulator for transmitting electrical signals from cathode and anodesignals.

A feature of a second embodiment of the invention for solving the abovedescribed problem is a detector module comprising a semiconductorradiation detector and a wiring board, wherein the semiconductorradiation detector comprises a plurality of semiconductor detectiondevices, each having a cathode electrode on one side of a semiconductordevice and an anode electrode on the other side arranged in parallel insuch a way that the cathode electrodes of the neighboring semiconductordetection devices are opposed to each other and an insulator which coatsat least a portion of the semiconductor detection devices from theoutside,

wherein the cathode electrode is connected to a first wiring provided onthe wiring board through a pin and the anode electrode is connected to asecond wiring provided on the wiring board through another pin.

Furthermore, a feature of a third embodiment of the invention forsolving the above described problem is a detector module comprising asemiconductor radiation detector and a first wiring board, wherein thesemiconductor radiation detector comprises a plurality of semiconductordetection devices, each having a cathode electrode on one side of asemiconductor device and an anode electrode on the other side, arrangedin parallel in such a way that the cathode electrodes are opposed toeach other and the anode electrodes are opposed to each other, a secondwiring board is disposed between the neighboring cathode electrodes, therespective cathode electrodes are connected to a plurality of secondwirings provided on the second wiring board, a third wiring board isdisposed between the neighboring anode electrodes and the respectiveanode electrodes are connected to a plurality of third wirings providedon the third wiring board,

wherein the semiconductor radiation detector is disposed on the firstwiring board, and

the second wiring of the second wiring board is connected to the firstwiring provided on the first wiring board and the third wiring of thethird wiring board is connected to a fourth wiring provided on the firstwiring board.

The second and third wiring boards preferably comprise a wiring boardhaving flexibility, for example, an FPC (Flexible Printed Circuit).

The present invention makes it possible to detect γ-rays by separatingtheir positions in the direction of incidence of γ-rays, too, andfurther detect positions separately in the three-dimensional direction.As a result, spatial resolution can be improved. Furthermore, the firstand second embodiments have another effect of allowing the semiconductorradiation detector to be replaced, for example, enabling a semiconductorradiation detector to be detached or attached individually. Furthermore,the third embodiment can arrange the semiconductor detection devicesextremely densely and consequently has the effect of improvingsensitivity, too.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a semiconductor radiation detectiondevice used for a semiconductor radiation detector according to a firstembodiment of the present invention;

FIG. 2 is a cross-sectional view showing the semiconductor radiationdetector according to the first embodiment of the present invention;

FIG. 3 is a plan view of the semiconductor radiation detector accordingto the first embodiment of the present invention;

FIG. 4 is a plan view of a detector module using the semiconductorradiation detector according to the first embodiment of the presentinvention;

FIG. 5 is an assembly diagram of the detector module using thesemiconductor detector according to the first embodiment of the presentinvention;

FIG. 6 is a perspective view of a detector module using a semiconductordetector according to a second embodiment of the present invention;

FIG. 7 is an exploded perspective view showing the semiconductorradiation detector in FIG. 6;

FIG. 8 is a longitudinal cross-sectional view of a PET-X-ray CTexamination apparatus provided with a PET examination apparatus usingthe detector module in FIG. 4 according to a third embodiment of thepresent invention;

FIG. 9 is a cross-sectional view showing a semiconductor radiationdetector according to a first modification example of the presentinvention;

FIG. 10 is a cross-sectional view showing a semiconductor radiationdetector according to a second modification example of the presentinvention;

FIG. 11 is a cross-sectional view showing a semiconductor radiationdetector according to a third modification example of the presentinvention;

FIG. 12 is a plan view showing a semiconductor radiation detectoraccording to a fourth modification example of the present invention;

FIG. 13 is a plan view showing a semiconductor radiation detectoraccording to a fifth modification example of the present invention;

FIG. 14 is an assembly diagram showing the semiconductor radiationdetector according to the fifth modification example of the presentinvention;

FIG. 15 is a plan view showing a semiconductor radiation detectoraccording to a sixth modification example of the present invention;

FIG. 16 is a plan view showing a semiconductor radiation detectoraccording to a seventh modification example of the present invention;and

FIG. 17 is an exploded diagram showing a pin insertion hole and elasticbodies, etc., according to an eighth modification example of the presentinvention.

DESCRIPTION OF THE EMBODIMENTS

With reference now to the attached drawings of FIGS. 1 to 5, a firstembodiment of the present invention will be explained below.

First Embodiment

Reference numeral 1 in FIG. 1 denotes a radiation detection device andthis radiation detection device 1 is constructed by including fivesemiconductor devices 2 (see FIG. 2) made up of a rectangular flat platemade of, for example, CdTe, cathode electrodes 3 (Pt, etc.) formed intoa thin-film shape on one side of each semiconductor device 2 by meansof, for example, vapor deposition, anode electrodes 4 (In, etc.) formedinto a thin-film shape on the other side of the semiconductor device 2and a rectangular parallelepiped elastic insulator 5 (see FIG. 2) whichcovers the five semiconductor devices 2 from the outside.

As shown in FIG. 2, this semiconductor radiation device 1 consists offive semiconductor devices 2 stacked together. Furthermore, conductivecathode-side thin plates 6 are pasted to the respective cathodeelectrodes 3 and conductive anode-side thin plates 7 are pasted to therespective anode electrodes 4. First and second internal wirings 8, 9provide connections among the thin plates 6 and the thin plates 7,respectively. Furthermore, rectangular parallelepiped brackets 5A, 5Aare formed integral with the insulator 5 on both sides in its widthdirection and pin insertion holes 5B are formed in these brackets 5A inthe longitudinal direction thereof so that a cathode pin 29 and an anodepin 30 which will be described later are inserted therein. Furthermore,a cathode terminal 10 to be connected to the first internal wiring 8 isexposed from an end face of the one bracket 5A to the outside and ananode terminal 11 to be connected to the second internal wiring 9 isexposed from an end face of the other bracket 5A to the outside. Thesemiconductor devices 2, cathode electrodes 3, anode electrodes 4,insulator 5, thin plates 6, 7, internal wirings 8, 9, cathode terminal10 and anode terminal 11 constitute a semiconductor radiation detector12. Note that the structures of the first internal wiring 8 and cathodeterminal 10, and the second internal wiring 9 and anode terminal 11 canbe simplified by forming inner walls of the respective pin insertionholes 5B using a conductive material and connecting the thin plates 6and 7 with the conductive inner walls.

In FIG. 4, reference numeral 21 denotes a wiring board used for thisembodiment and first cathode wirings 22 arranged in parallel to oneanother, a second cathode wiring 23 which extends perpendicular to therespective cathode wirings 22 and connects the cathode wirings 22 and athird cathode wiring 24 which extends rightward from the cathode wiring22 at the top end in FIG. 4 are buried in this wiring board 21. Thesecathode wirings 22, 23 and 24 are electrically connected and the samepotential is supplied from the outside of the wiring board 21 to thecathode electrodes 3 of all the detectors. The plurality ofsemiconductor radiation detectors 12 and the wiring board 21 in whichthese semiconductor radiation detectors 12 are arranged constitute adetector module 42. The detector module 42 also includes a plurality ofcathode wiring and a plurality of anode wirings.

Furthermore, first anode wirings 25 arranged parallel to one another,second anode wirings 26 arranged parallel to one another, third anodewirings 27 arranged parallel to one another and fourth anode wirings 28arranged parallel to one another are buried in the wiring board 21.

Then, as shown in FIG. 4 and FIG. 5, cathode pins 29 are formed in anupright position on the cathode wiring 22, spaced substantiallyuniformly on one side and the other side of the wiring board 21.Furthermore, anode pins 30 are also formed in an upright position at theends of the first, second, third anode wirings 25, 26, 27 spacedsubstantially uniformly on one side and the other side of the wiringboard 21.

Then, the semiconductor radiation detector 12 is inserted in adetachable manner in the direction indicated by an arrow A in FIG. 5with a cathode pin 29 and an anode pin 30 fitted in the pin insertionholes 5B, 5B of the elastic insulator 5 with clamping margins. Thesemiconductor radiation detector 12 may also be directly fixed to thewiring board 21 using a conductive space, etc., instead of the cathodepin 29 and anode pin 30. In this case, instead of the pin insertionholes 5B, the insulator 5 is provided with plated wiring and the ends ofthis plated wiring are used as a cathode terminal 10 and an anodeterminal 11. A conductive paste, etc., may be applied to these cathodeterminal 10 and anode terminal 11, which may be then fixed to the wiringboard 21.

Then, the operation of the semiconductor radiation detector 12 havingsuch a structure will be explained.

A negative voltage is applied to the cathode electrodes 3 of thesemiconductor device 2 from the outside of the wiring board 21 throughthe cathode wirings 22, 23, 24, a reverse bias voltage is formed betweenthe cathode electrodes 3 and anode electrodes 4 of the semiconductordevice 2 so that γ-rays can be measured. When γ-rays enter thesemiconductor device 2, electric charge is induced between the cathodeelectrodes 3 and anode electrodes 4 set in the semiconductor device 2,and signals corresponding to the amount of charge induced are outputfrom the anode wirings 25, 26, 27, 28 to the outside through a thinplate 7, internal wiring 9, anode terminal 11 and anode pin 30.

This embodiment allows γ-rays to be detected by separating theirpositions in the direction of incidence of γ-rays, too, and furtherallows γ-rays to be detected with their positions separated in thethree-dimensional direction. Furthermore, covering with an insulatorfacilitates handling of the semiconductor radiation detector inmanufacturing, etc., and can physically protect the radiation detectiondevices.

Furthermore, according to the method of using the cathode pin 29 andanode pin 30, the semiconductor radiation detector 12 is mounted on thewiring board 21 in a detachable manner, and it is possible to therebyreplace any semiconductor radiation detector 12 and improve operability,etc., in the case of replacement.

Furthermore, the entire semiconductor device 2 is covered with theinsulator 5, and therefore it is possible to produce the moisture-proofeffect and light-shielding effect on the semiconductor radiationdetector 12.

Second Embodiment

Then, a second embodiment of the present invention will be explainedwith reference to the attached drawings of FIG. 6 and FIG. 7. In FIG. 6,a plurality of semiconductor radiation detectors 31 are constructed byincluding thin wiring boards 32 with flexibility called “FPC (Flexibleprinted circuit)”, semiconductor devices 33 mounted on both sides of thethin wiring boards 32, cathode electrodes 34 formed in a thin-film shapeon one side of the semiconductor devices 33 through vapor deposition,etc., and anode electrodes 35 formed on the other side of thesemiconductor devices 33.

The semiconductor devices 33 are arranged in four rows in the directionin which γ-rays propagate with a small gap interposed betweenneighboring devices and also arranged in four rows in the directionorthogonal to the direction in which γ-rays propagate with a small gapinterposed between neighboring devices. Furthermore, the semiconductorradiation detectors 31 are mounted fixed to both sides of a thick wiringboard (FR-4, etc.) 36. A plurality of semiconductor radiation detectors31 mounted on both sides of the thick wiring board 36 constitute adetector module 43. Note that it is also possible to construct thesemiconductor devices 33 using one crystal on the same plane and bydividing only the electrodes.

Furthermore, in the thin wiring boards 32 interposed between the facinganode electrodes 35, 35, four signal lines 38, 39, 40 and 41, whichextend to the positions corresponding to the anode electrodes 35 of therespective semiconductor devices 33 to be connected to the respectiveanode electrodes 35 are buried as shown in FIG. 7.

On the other hand, in the thin wiring boards 32 interposed between thefacing cathode electrodes 34, 34, supply lines (not shown) for applyinga voltage common to all cathodes are buried in the cathode electrodes 34and these signal lines are connected to the cathode electrodes 34 of theplurality of semiconductor devices 33 arranged along the direction ofincidence of γ-rays.

The above described supply lines connected to the cathode electrodes 34are connected to cathode wiring (not shown) of the thick wiring board 36and the signal lines 38, 39, 40 and 41 are connected to the respectiveanode wirings (not shown) of the thick wiring board 36.

Note that the thick wiring boards 36 may be replaced by the thin wiringboards 32.

This embodiment having such a structure can also detect γ-rays byseparating positions in the three-dimensional direction as with thefirst embodiment. Furthermore, it is also possible to reduce spacingbetween the plurality of semiconductor devices 31 and improvesensitivity.

Third Embodiment

Then, a third embodiment of the present invention will be explained withreference to the attached drawing of FIG. 8. The same components in thisembodiment as those in the first embodiment are assigned the samereference numerals and explanations thereof will be omitted.

As shown in FIG. 8, a PET-X-ray CT examination apparatus 100, which is aradiation imaging apparatus, comprises an X-ray CT examination apparatus101 and a PET examination apparatus 102 side by side. Furthermore, thePET-X-ray CT examination apparatus 100 includes a bed holding section103 and a movable bed 104 provided on the bed holding section 103. Then,the X-ray CT examination apparatus 101 is provided with an X-ray CTgantry 105 having an opening 105A, a rotary section 106 rotatablymounted in the X-ray CT gantry 105, an X-ray generator 107 provided inthe rotary section 106 and a radiation detector 108, which is ascintillator detector provided in the rotary section 106. Then, thisX-ray CT examination apparatus 101 measures X-rays which are emittedfrom the X-rays generator 107 and have passed through an examinee Pusing a signal processing section (not shown) and obtains a mode imageof the interior of the examinee P.

Furthermore, the PET examination apparatus 102 includes a PET gantry 110having an opening 110A and the PET gantry 110 has a plurality ofdetector modules 42 arranged in the circumferential direction and axialdirection. For this reason, a plurality of radiation detectors 12 arealso arranged in the circumferential direction and axial direction ofthe PET gantry 110. The PET examination apparatus 102 is a radiationimaging apparatus which marks radionuclides which emit positrons throughnucleorrhexis in chemicals, administers the chemicals into the examineeP, captures pairs of γ-rays having 511 keV energy which are emitted whenpairs of positron and electron are annihilated in the body of theexaminee P and creates images of them as functional images.

This embodiment having such a structure can mount the semiconductorradiation detectors 12 densely on both sides of the wiring board 21 asdescribed in the conventional art, thereby increase the density of thesemiconductor radiation detectors 12 per a unit length of the wiringboard 21 in the detector module 42, improve the detection sensitivityand improve the performance and reliability of the PET-X-ray CTexamination apparatus 100.

The PET examination apparatus 102 may also mount the detector module 43shown in FIG. 6 in the PET gantry 110 instead of the detector module 42as with the detector module 42.

As shown in FIG. 5, the first embodiment has described the case wherethe terminals of both the cathode terminal 10 and anode terminal 11 areexposed from one side of the insulator 5 which is a rectangularparallelepiped and the semiconductor radiation detectors 12 are fixed toboth sides of the wiring board 21 using the cathode pin 29 and anode pin30 as an example.

However, the present invention is not limited to this but can be adaptedso that as shown in a first modification example shown in FIG. 9, acathode pin 51 is inserted from one side of an insulator 54 of asemiconductor radiation detector 50 and an anode pin 55 is inserted fromthe other side of the insulator 54 of the semiconductor radiationdetector 50. In this case, the cathode pin 51 is connected to a cathodewiring 22 buried in a wiring board 21A and the anode pin 55 is connectedto an anode wiring 25 buried in a wiring board 21B.

Furthermore, for example, as a second modification example shown in FIG.10, it is also possible to adopt a structure in which a semiconductorradiation detector 50A is placed in a direction perpendicular to awiring board 21, and a cathode pin 51 and an anode pin 55 disposed onthe wiring board 21 in an upright position are inserted into thesemiconductor radiation detector 50A.

Furthermore, in a semiconductor radiation detector 50B which is a thirdmodification example shown in FIG. 11, a plurality of radiationdetection devices 1 are arranged in a staggered configuration andinternal wirings 62 are connected to anode electrodes of the radiationdetection devices 1 protruding in one direction out of these radiationdetection devices 1. Furthermore, internal wirings 61 are connected tocathode electrodes of the radiation detection devices 1 protruding inthe other direction out of these radiation detection devices 1. Thecathode pin 51 and anode pin 55 are connected to these internal wirings61, 62.

The first embodiment has described the case where a plurality ofsemiconductor radiation detectors 12 are mounted on the wiring board 21independently of one another through gaps as an example, but the presentinvention is not limited to this and can be adapted as a fourthmodification example shown in FIG. 12 so that insulators 71 ofneighboring semiconductor radiation detectors 70 are united.

The first embodiment has also described the case where the entiresemiconductor radiation detector 1 is coated with the insulator 5 as anexample, but the present invention is not limited to this and can beadapted so that as in the case of a fifth modification example shown inFIG. 13 and FIG. 14, for example, a semiconductor radiation detector 80is provided with insulators 81, 82 partially having pin insertion holes81A, 82A and cathode socket (e.g., hollow metal pipe) 83 and anodesocket 84 are provided inside the pin insertion holes 81A, 82A of thisinsulator 81 so that the cathode pin 85 is inserted into the cathodesocket 83 and the anode pin 86 is inserted into the anode socket 84.

In this case, it is also possible to adopt a structure as a sixthmodification example shown in FIG. 15, for example, in which twoneighboring semiconductor radiation detectors 90, 90 are partiallyprovided with insulators 91, 92 and the two semiconductor radiationdetectors 90, 90 are kept insulated from each other by means of a commoninsulating plate 93.

Furthermore, it is also possible to adopt a structure as a seventhmodification example shown in FIG. 16, for example, in which a pininsertion hole 94A on the cathode side is provided at one end of acommon insulator 94 attached to two neighboring semiconductor radiationdetectors 90 and pin insertion holes 94B, 94B on the anode side areprovided at the other end of the insulator 94.

Moreover, the first embodiment has described the case where the cathodepin 29 and anode pin 30 having a slightly greater diameter than thediameter of the pin insertion holes 5B are fitted into these pininsertion holes 5B utilizing elasticity thereof as an example, but thepresent invention is not limited to this and, for example, as in thecase of an eighth modification example shown in FIG. 17, hemisphericalelastic bodies 95, 95 are attached to the inner surfaces of a pininsertion hole 5B′ and a cathode pin 29 or anode pin 30 is inserted intoa pin insertion hole 5B′ in such a way as to be pushed by the elasticbodies 95, 95 from both sides.

In the above described modification examples, if detachability is notessential, it is possible to directly fix semiconductor radiationdetectors to the wiring board using not the aforementioned cathode pinand anode pin but a conductive paste, etc. In this case, instead of pininsertion holes, plated wiring is applied to the insulator 5 and theends of this plated wiring are used as a cathode terminal 10 and anodeterminal 11. A conductive paste, etc., may be applied to this cathodeterminal 10 and anode terminal 11 and fixed to the wiring board 21.

Furthermore, in the first embodiment, the output ends of the anode andcathode of the semiconductor radiation detector are arranged at diagonalpositions of the semiconductor device, but their positions are notlimited to this and their output ends may be arranged on the same sideof the semiconductor detection device and a wiring pattern correspondingto the output end positions may be used for the wiring board in thiscase.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A semiconductor radiation detector comprising: a plurality ofsemiconductor detection devices, each having a cathode electrode on oneside of a semiconductor device and an anode electrode on the other side,arranged in parallel; and an insulator which coats at least a portion ofsaid semiconductor detection devices from the outside. 2-21. (canceled)